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In this research, we present an approach to identify variable characteristics of an inhomogeneous thermoelectroelastic radially polarized elongated hollow cylinder. The cylinder's thermomechanical characteristics depend on the radial coordinate. We consider two loading types for the cylinder—the mechanical and the thermal ones. The radial displacement is considered as the additional data collected on the outer cylinder's surface under the first type load, while the temperature measured over a certain time interval is considered for the second type load. The direct problem after non-dimensioning and applying the Laplace transform is solved by jointly applying the shooting method and the transform inversion based on expanding the actual space in terms of the shifted Legendre polynomials. The effect of the laws of change in variable characteristics on the input data values taken in the experiment is analyzed. A nonlinear inverse problem on the reconstruction of the cylinder's variable properties is formulated and solved on the basis of an iterative technique. The initial approximation is set in the class of positive bounded linear functions whose coefficients are determined from the condition of minimizing the residual functional. To find the corrections at each stage of the iterative process, the Fredholm integral equations of the first kind are solved by means of the Tikhonov method. A series of computational experiments on recovering one and two variable characteristics is conducted. The effect of coupling parameters and input noise on the reconstruction results is revealed. [ABSTRACT FROM AUTHOR]

The results are based on the first principle modeling and calculations of hydroxyapatite (HAP) nanostructures, especially in ordered hexagonal phase. HAP structures were studied using Local Density Approximation (LDA) method with calculations of Density of States (DOS) and molecular modeling by HyperChem. Computed data show that monoclinic and hexagonal phases can coexist, especially in the ordered states. Calculated piezoelectric coefficient for hexagonal phase d33 ∼6.4 pm/V is consistent with previously obtained value for monoclinic HAP (15.7 pm/V) and experimental data. The estimated pyroelectric coefficient at the order of γ ∼ 10–100 μC/(m2K) is also in line with experimental data. [ABSTRACT FROM AUTHOR]

Dynamic scanning photocurrent microscopy was applied to Sb2Se3 crystalline single nanowires (NWs) to analyze their transient photocurrent responses. These NWs exhibited switching behavior with rapid rise and decay times upon illumination by laser pulses. The estimated spectral responsivity and external quantum efficiency for a freshly-prepared NW at a bias voltage of 0.3 V and excitation wavelength of 488 nm were ∼16.9 mA/W and ∼42.9%, respectively. A pyroelectric-like current transient was observed with reduced spectral responsivity when nonpolar Sb2Se3 single-crystalline NWs were excited by laser pulses. Because Sb2Se3 NWs were nonpyroelectric or ferroelectric, the pyroelectric-like current could possibly be attributed to temperature dependent nonlinear space-charge distributions. Defects produced by the external electrical bias generated and re-distributed space charges in the NWs. As a result, the temperature dependent inhomogeneous electric field led to nonlinear expansions or contractions of the lattice (electrostriction) that can produce pyroelectric current. We obtained a lower bound of equivalent pyroelectric coefficient α ≥ 60.09 μC/m2 K from these materials by fitting the electrical transients. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Compositionally graded Pb(Zr,Ti)O 3 thin films were prepared on platinum-coated silicon substrates by a modified Sol-Gel method and rapid heat-treatment. The composition depth profile of a typical up-graded film was determined by using a combination of auger electron spectroscopy and Ar ion etching. The results confirm that the processing method produces graded composition change. XRD analyses show that the graded thin films possess composite structure of tetragonal and rhombohedral. The dielectric constants of the graded thin films are higher than that of every unit thin films, but loss tangent are similar each other at 10 kHz. The dielectric constants of the up-graded and down-graded films at 10 kHz were found to be 206 and 219, respectively. The Hysteresis loops of the graded thin films showed fine ferroelectric properties. The remnant polarizations (Pr) of the up-graded and down-graded films were 24.3 μC/cm 2 and 26.8 μC/cm 2 , respectively. The pyroelectric coefficients of the graded thin films were higher than that of every unit thin film. The pyroelectric coefficients of the up-graded and down-graded films were 57.8 and 46.1 nC/cm 2 K at room temperature, respectively. [ABSTRACT FROM AUTHOR]

Triglycine sulfate crystals (TGS) doped with l- and d-alanine, respectively, where grown in paraelectric phase at 52 °C. They show stable parameters versus pure TGS crystals, lower permittivities and losses, i.e. higher pyroelectric figure of merit. l- and d-alanine-doped crystals show a mirror asymmetry of the growth habit along the ferroelectric axis. Hysteresis loop of pure and doped samples were automatically recorded. Internal bias field of about 1 kV/cm, induced by the two dopants, stabilizes the polarization components P+ and P- in opposite directions. Spontaneous polarization of doped crystals shows two unequal P+/P- components, having a peculiar dependence on the ac applied electric field. Dopage simulation of pure TGS samples, using several bias fields, shows even more complicated pattern.Pyroelectric coefficients were evaluated from pyroelectric current measurements. A remarkable asymmetry of the pyroelectric coefficient peak values for the enantiomorphous-doped crystals was noticed, crossing up and down the Curie point. This fact suggests a non-equivalent l/d-alanine dopant substitution of the glycine group GI in the host lattice. It has been shown that the pyroelectric coefficient can be increased at room temperature, under an optimized dc electric field applied on the pyroelectric wafer. Doped crystals are suitable for IR detector and for more stable gas sensors applications in pollution monitoring. [Copyright &y& Elsevier]